In the prior art, it is known to provide a flexible tubular shaft for mounting a microphone. The flexible tubular support shaft can be flexed or bent into different curved shapes to allow the microphone to be adjusted to a desired position. Typically, an adjustable microphone support shaft comprises a pair of elongated helical elements each including a plurality of coils which are wound together along a common longitudinal axis. The coils engage each other with sufficient friction to allow the flexible support shaft to retain its bent shape and to hold the microphone in the desired position. Similarly, it is known to employ such flexible support shafts to mount adjustable lamps and fiberoptics devices.
In the case of flexible support shafts for microphones, it is desirable to provide a shaft construction which is capable of bending over a wide range of angles to facilitate the adjustment of the microphone into its desired position. No provision is made to impose a limit on the angle of bending of the flexible support shaft because of the advantages associated with a wide range of adjustment. Thus, the conventional microphone support shafts are not suitable for applications in which a limit on the bending range is required.
In co-pending U.S. patent application Ser. No. 832,299, filed on Feb. 7, 1992, entitled "Surgical Anastomosis Stapling Instrument With Flexible Support Shaft And Anvil Adjusting Mechanism", assigned to the same assignee as the present invention, a surgical stapling instrument including a flexible shaft assembly is disclosed. The flexible shaft assembly comprises a pair of elongated helical elements which are concentrically wound together with the coils of the first helical element alternately interspersed with the coils of the second helical element. Each coil of the first helical element has a round cross section and each coil of the second helical element has a triangular cross section provided with sloped surfaces which slidably engage the adjacent round coils. There is, however, no disclosure of any mechanism to limit the bending of the flexible shaft assembly.
Accordingly, it is an object of the present invention to provide a flexible support shaft assembly which is capable of bending transversely relative to its longitudinal axis or centerline with a predetermined limit on the bending range.
Another object of the invention is to provide a flexible support shaft assembly comprising a pair of helical members which are wound together along a common axis with the coils of the helical members interspersed and adapted to limit the transverse bending of the support shaft assembly.
It is also an object of the invention to provide a flexible tubular support shaft assembly comprising a dual coil structure in which a pair of helical members are coiled together and adapted to limit the bending range of the support shaft assembly for use in a device such as a surgical stapling instrument.